Electrolysis of several aqueous solutions is carried out using a 9-V battery and pencil leads as electrodes. Because only the electrodes are shown in the videos, it is important to show these still images

or describe how the reactions were performed if students are to make sense of the videos. In each case the anode is on the left and a 9-V battery has been connected to the lead of each of the pencils near the eraser end with an alligator clip.

A Simplified Model To Predict the Effect of Increasing Atmospheric CO2 on Carbonate Chemistry in the OceanBrian J. Bozlee, Maria Janebo, and Ginger JahnThe chemistry of dissolved inorganic carbon in seawater is reviewed and used to predict the potential effect of rising levels of carbon dioxide in the atmosphere. It is found that calcium carbonate may become unsaturated in cold surface seawater by the year 2100, resulting in the destruction of calcifying organisms such as coral.Bozlee, Brian J.; Janebo, Maria; Jahn, Ginger. J. Chem. Educ.2008, 85, 213.

Molecular Models of EDTA and Other Chelating AgentsWilliam F. ColemanDeirdre Bell-Oudry presents a variation on an old theme in her paper on using an indirect EDTA titration for sulfate analysis (1). EDTA and (often loosely) related species are this month's Featured Molecules.EDTA is a hexaprotic acid (H6Y2+) having the pKa values given in the featured paper (1). Figure 1 shows a distribution diagram for the EDTA system (2). At the pH of normal waters, the predominant species have one or both of the nitrogen atoms protonated.Complexation, however, requires that both nitrogens be deprotonated and it is generally assumed that the form that complexes with metal ions is Y4−. Structures of several forms of EDTA are included in the molecule collection (Figure 2). These structures are quite flexible having many conformations that are readily accessible at room temperature.An introduction to EDTA chemistry leads to broader questions of metal ion chelation or sequestration. Related chelating agents included in the molecule collection are EGTA, DCTA, NTA, BAPTA, and DTPA. Molecular dynamics and Hartree-Fock calculations on BAPTA (Figure 2) confirm that many conformations, ranging from those with the phenyl rings parallel to one another, to more elongated forms, are essentially isoenergetic in room temperature aqueous solution (3).Also included in the molecule collection are several crown ethers, an isophore (nonactin), and a cryptand. These not only provide students with a glimpse of the types of molecules being employed for metal ion sequestration but open a wide range of topics of current research in a variety of areas of inorganic, industrial, environmental, and biological chemistry.